The invention relates to driving of accessories of an combustion engine, particularly an automobile internal combustion engine, using a combination pulley and speed reducer for increased efficiency and economy of engine operation.
The emphasis on conservation of energy has accelerated the development of higher fuel efficient automobile engines. Substantial waste exists in the accessory drive. Conventional accessories such as the air conditioner, power steering, alternator, and water pump,etc., are driven directly off the crankshaft which runs through a wide range of speeds. Accessories are designed to perform when the engine is idling. When the vehicle is running at cruising speed, the engine will run several times its idling speed and so will the accessories driven by it. Proportionally substantial power is wasted as engine speed increases, especially in highway driving. Therefore, saving this wasted power becomes a problem to which increased attention needs to be given.
Prior devices have been proposed for altering the speed ratio of a crankshaft of an internal combustion engine to an associated accessory drive. For example, U.S. Pat. Nos. 4,706,520; 4,653,349; 4,305,488; 4,265,135; 3,108,494 and 2,153,856 all disclose different devices for altering the speed of vehicle accessory drives. U.S. Pat. No. 4,706,520 uses a planetary gear train and a cone clutch which selectively engages a ring gear of the gear train to provide a direct drive, or underdrive or overdrive. U.S. Pat. No. 4,653,349 discloses a cone drive and engagable speed change ring which causes a desired ratio between crankshaft and accessory drive speeds. U.S. Pat. No. 4,265,135 discloses a complicated arrangement of a planetary gear train including ring gear, friction brake, friction clutch, and hydraulic system to provide a direct drive, constant speed drive, and high variable speed drive. U.S. Pat. No. 4,305,488 discloses a speed reducing planetary gear train in which a flywheel is clutched to the ring gear so that the flywheel overruns the ring gear when the vehicle is braked to drive the vehicle accessories even when the vehicle is stopped. U.S. Pat. No. 2,153,856 discloses a gear set for reducing the speed ratio of a vehicle accessory drive wherein different diameter sun gears are clutched together with ratchet teeth for a direct drive. While the above are illustrative of various and diverse proposals for solving the problem of inefficient vehicle accessory drives, they are not entirely satisfactory because of the complexity of the devices, lack of interchangeability with the conventional crankshaft pulley arrangement and accessory drives, unsuitability for reliable actuation in response to speed conditions, and other reasons that will become apparent from an understanding of the advantages of the present invention.
Speed reducing devices are known in many industrial applications. The inventor of the present invention has been issued U.S. Pat. Nos. 3,122,945 and 4,189,962 related to industrial applications, and U.S. Pat. No. 4,056,018 relating to a speed reducer for a heavy-duty vehicle wheel drive typically used in off-road equipment. Industrial speed reducing drives have not been utilized effectively in the motor vehicle field for many reasons. The main power transmission drive of a motor vehicle is too complex and different, particularly the manually clutched transmission, to be germane. The accessory drives of motor vehicles have quite different input and output arrangements and requirements, not to mention the rigorous environments of combustion engine drives and vehicular use. Industrial applications typically use variable speed electric motors and a single gear ratio reducer to obtain variable speed drives and reduction. The above noted U.S. Pat. No. 3,122,945 relates to an epicyclic gear arrangement having a pulley input driven by an electric motor in an industrial application for speed reduction, however, the arrangement is not suitable for motor vehicle use.
Accordingly an object of the present invention is to provide a variable speed accessory drive for an internal combustion engine which is simple and reliable in construction and operation.
Another object of the present invention is to provide a combination pulley and speed reducer which may be easily substituted for a conventional accessory drive pulley on a power crankshaft for varying the speed of the accessory drive.
Another object of the present invention is to provide a speed reducing drive for vehicle accessories which may be easily and reliably switched at a predetermined vehicle speed from direct drive to reduced drive and vice versa.
Still another object of the present invention is to provide a speed reducing gear train for coupling a vehicle crankshaft to an accessory drive which has a minimum of parts and may easily exchange the crankshaft and operate at direct and reduced drives.